1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer or a copying machine that forms an image by an electrophotographic process and, in particular, to an apparatus having various electric substrates.
2. Related Background Art
An example of a configuration of functional components in a conventional laser printer is shown in FIG. 5. FIG. 5 is a sectional view of a conventional image recording apparatus. As shown in FIG. 5, the image recording apparatus has an engine control substrate 11 for controlling a printer engine, an image controller substrate 12 for generating bit map data to modulate ON/OFF a semiconductor laser based on image data sent from a host computer (not shown), a scanner unit 13 constituted by a semiconductor laser, a laser driving circuit, a horizontal synchronizing signal generation circuit, a polygon motor, a lens, a turnback mirror or the like, a process cartridge 14 constituted by a photosensitive drum, a charging roller, a developing device, a cleaner container or the like, a conveying path 15 for feeding and conveying a recording sheet, and a motor 16 functioning as a driving source for driving means for driving the conveying path 15.
In the image recording apparatus having the structure shown in FIG. 5, the engine control board 11 is arranged in a planar state below the conveying path 15, the image controller board 12 is arranged further below the engine control board 11, the scanner unit 13 is arranged above the conveying path 15, and the process cartridge 14 is arranged between the conveying path 15 and the scanner unit 13.
FIG. 6 is a functional block diagram of each circuit board. As shown in FIG. 6, the engine control board 11 is constituted by a switching power supply circuit part 11a, a motor driver circuit part 11b for performing sheet conveyance driving or the like, a high voltage power supply circuit part 11c necessary for an electrophotographic process, and an engine control circuit part 11d including a processor for controlling each driving circuit.
In addition, the image controller board 12 is constituted by a processor for generating bit map data to modulate ON/OFF the semiconductor laser based on image data from the host computer and communicating with an engine control circuit, a control ROM, an RAM 12a for temporarily storing the bit map data or the like.
The scanner unit 13 is constituted by a semiconductor laser driving circuit part 13a for driving the semiconductor laser based on the ON/OFF data from the image controller board 12, a polygon scanner 13b for horizontally scanning laser beams from the semiconductor laser on the photosensitive drum, a not-shown BD sensor for generating a horizontal synchronizing signal, and the like. The above is an example of the structure of the conventional image recording apparatus such as a laser printer.
However, in the above-mentioned conventional image recording apparatus, the engine control board 11 and the image controller board 12 are arranged in a planar state below the conveying path 15, and the scanner unit 13 is arranged above the conveying path 15. Thus, the engine control board 11 or the image controller board 12 and the scanner unit 13 are connected by a bundled line (cable or jumper) 17, FFC, or the like. Since the engine control substrate 11 or the image controller substrate 12 and the scanner unit 13 are arranged far from each other, wiring for them is long. In particular, since high resolution of a laser printer has been advanced in recent years, a frequency of a laser ON/OFF signal (VDO) has also become high. As a result, radiation field noises (RFI) have increased, and it tends to be difficult to cope with the radiation field noises.
In order to cope with the radiation field noises, a ferrite core is used in a bundled line or a shield electric wire is used, which leads to significant increase in costs.
Moreover, in the conventional image recording apparatus shown in FIGS. 5 and 6, the switching power supply circuit part 11a with a large heat value is arranged horizontally on a bottom surface of a main body of the image recording apparatus. Thus, heat radiation efficiency is low, and harmful effects such as deterioration of components and decrease in quality of an image due to increase in temperature in the apparatus are likely to occur. In addition, using air cooling means such as a fan in order to avoid the harmful effects leads to increase in costs.
An object of the present invention is to provide an image forming apparatus in which a high-frequency wiring part can be shortened to realize reduction of radiation field noises and costs for coping with the noises, and at the same time, heat radiation efficiency can be increased to prevent deterioration of components, degradation of an image quality, and the like due to increase in temperature in the apparatus.
Another object of the present invention is to provide an image forming apparatus including a driving circuit substrate for driving an apparatus main body, a control circuit substrate for controlling the apparatus main body, and an image controller substrate for controlling image data, in which the driving circuit substrate is connected to the control circuit substrate, and the control circuit substrate is connected to the image controller substrate, and in which the driving circuit substrate and the image controller substrate are provided substantially vertically, and the control circuit substrate is provided substantially horizontally.
Further objects of the present invention will be apparent in the following description.